1. Chemical Compostition
Ms. Moore Chemistry

2. Atomic Mass Atomic Mass Unit – 1/12 of the mass of a 12C atom
1 atom C = 1.99 x g
Difficult to handle
6 protons, 6 neutrons and 6 electrons
Mass of proton & neutron is almost equal to 1 amu
Mass of Proton = 1.67 x g = 1 amu
Mass of electron = 9.11 x g = amu
Average Atomic Mass
Periodic Table
Weighted Average mass of all known isotopes

3. Mass Calculations Simple Mass Calculations
What is the mass of 75 Aluminum atoms?
How many Sodium atoms are contained in amu?

4. Mole Atoms are tremendously small Special names for large quantities
Unit of measurement for atoms
Provide a count to mass relationship
Dozen, Peck, Gallon are examples

5. Mole Short for molecules # of atoms found in exactly 12 grams of 12C
Avogadro’s Number

6. Mole 6.022 x 1023 representative particles
Representative particle – any species commonly found in a substance
1 Mole of any substance

7. Mole Calculations Use Dimensional Analysis 6.022 x 1023 atoms = 1 mol
How many atoms of Silver are present in 1.50 mol of Silver?

8. Mole Calculations
How many molecules of water are found in 2.5 moles of water?
How many moles of Oxygen are present in 8.91x1024 molecules?

9. Mole Calculations Moles can be used in compounds 1 mole of H2O
2 moles of Hydrogen
1 mole of Oxygen
1 mole of H2SO4
1 mole of Sulfur
4 moles of Oxygen

10. Mole Calculations Ions can be represented as moles 1 mole of Pb(NO3)2
1 mole of Pb+2 ions
2 moles of NO3- ions
1 mole of Cu3(PO4)2
3 moles of Cu+2 ions
2 moles of PO4-3 ions

11. Mole Calculations
How many moles of Nitrate are found in 4.54 x 1024 formula units of Potassium Nitrate?
How many sulfate ions will be found in 3.22 moles of Aluminum Sulfate?
4th Period : 01/20/10

12. Mass Relationship Relationship to mass
# of atoms present when the atomic mass of an element is expressed in grams
40.08 g Ca = 1 mol Ca = x 1023 atoms Ca
107.9 g Ag = 1 mol Ag = x 1023 atoms Ag
207.2 g Pb = 1 mol Pb = x 1023 atoms Pb

13. Molar Mass Mass of 1 mol of an element or compound
Taken from Periodic Table for elements
6th Period : 01/22/10

14. Mole-Mass Calculations
How many moles are contained in 75.0 g of Nickel?
How many moles are contained in 50.0 g of Magnesium?

15. Gram-mole-atom 2nd : 01/28/13 3rd : 01/29/13 4th : 01/28/13

16. Mass-Atoms Relationship
How many atoms are present in 75.0 g of Iron?
4th Period : 01/26/10

17. Mass-Atoms Relationship
How many grams are in 4.33x1024 atoms of Calcium?
1st : 01/31/12
2nd : 01/30/12
4th : 01/30/12

18. Moles in Molecules Formula Mass of Molecules and Ionic Compounds
Sum of the number of moles of all elements times atomic mass
1 mole CO2
1 mole Carbon (12.01 g/mol) = g
2 mole Oxygen (16.00 g/mol) = g
Total Mass = g

19. Formula Weight
AlBr3
NaHCO3
SiF4
Cu3(PO4)2
4th period: 02/01/12

20. Percent Composition % by mass of each element in compound
Determine total mass of 1 mole of compound
Molar Mass
Determine mass of each element

21. Percent Composition % by mass of each element in compound
Determine total mass of 1 mole of compound
Molar Mass
Determine mass of each element

22. Percent Composition Any part of a whole
Determine the %water in CuSO4·5H2O
2nd : 01/30/13
7th : 01/31/13

23. Percent Composition
Nitrogen is a key component of fertilizers. The most abundantly used fertilizer is Ammonium Nitrate. Determine the % Nitrogen in Ammonium Nitrate.
1st : 02/03/12
2nd : 02/06/12
4th : 02/06/12
7th : 02/03/12

24. Percent Composition Highest Content of an element
Compare % compositions
Which of the following has the highest Phosphorus content?
Na3PO4
Ca3(PO4)2
(NH4)3PO4
K3PO4
3rd : 02/01/13

25. Empirical Formula Lowest ratio of atoms in a compound C6H6 - Benzene
C2H2 – Acetylene
Empirical Formula : CH
C6H12O6 – glucose
CH2O – formaldehyde
Empirical Formula : CH2O

26. Empirical Formula Formula is given in small, whole # ratios
Need grams to convert to moles
Divide all moles by the smallest # (create ratios)
Determine the empirical formula of a compound which is % Carbon, 53.3% Oxygen and the remaining portion is Hydrogen.
1st : 02/07/11

27. Empirical Formula
A sample of Aluminum Oxide contains g of Aluminum and g of oxygen. What is the empirical formula of the compound?
2nd : 02/08/11

28. Empirical Formula General Steps Determine the mass of each element
Calculate moles
Determine the smallest # of moles
Divide each mole by the smallest # of moles
At least one element will always be 1
If necessary, use an integer to convert all #’s into whole #’s

29. Empirical Formula
Determine the empirical formula for Cisplatin if it contains % Pt, 9.34% N, 2.02% H and 23.63% Cl.
02/03/11

30. Molecular Formula Empirical Formula
Determined from Composition of Compound
Molecular Formula
Need Molecular Weight (Molar Mass)
Can be same as Empirical Formula
Relationship is always integer multiplier

31. Molecular Formula
A compound has an empirical formula of CH2 and a molecular weight of 56.1 g/mol. What is the molecular formula?
2nd : 02/04/13
4th : 02/04/13

32. Molecular Formula
A compound is 92.3% C and 7.7% H and has a Molecular Weight of 78.0 g/mol. What is the molecular formula?